are you saving the file as a sgu or mgu in the save as dialogue and then closing? once closed can you open it in BIAB? i'm not sure what you mean by 'saving onto utility tracks'.

i rarely use BIAB for anything other than roughing out a song but would have thought if you use RB to save yuor project as a BIAB file, then close, when you open it with BIAB, BIAB should sort out where it puts the midi parts.

but as i say, i don't use BIAB much, i do most work in RB. maybe a BIAB expert can help but if you were trying to load from RB into BIAB without saving and closing the file i am not sure what would happen.